Module manifest should support JSON in addition to XML

There should be backward compatibility so we always first check for the existence of module.json and if not present, fall back to module.xml.
With JSON would be good to have a schema as well available in github that users can link to using $schema and get intellisense.
For server-side editing, would want a new studio document to view the JSON version.

Internal issue: HSIEO-6645.

Related to #502